chapotraphouse

It's hands down gross negligence on the part of Panera. I'm surprised so many people are leaping to defend a corporation that did something harmful as a marketing gimmick and had it backfire by killing or causing kidney failure in customers. They are serving this from the soda fountain setup in fountain drink containers, which means there is no nutritional/supplement facts and FDA warning label provided on every container like with drink cans/bottles. Panera created this product without ever wondering why both Coca-Cola and Pepsi soda fountain energy beverages have their caffeine concentration formulated not as coffee/energy-drink strength but tea/soda strength to account for the standard serving size. It's the same reason soda fountain energy beverages always have the vitamin B concentration dramatically lower than that of canned energy drinks or energy shots because Coca-Cola and Pepsi are well aware someone drinking fountain drink servings of those vitamins can cause kidney damage.

Is this literally just a case of "people who drink coffee build up a tolerance to both the taste and caffeine, while anyone can just chug a literal gallon of sugar water with no caffeine tolerance at all"?

400 mg per liter isn't all that high, that's a little higher concentration than coffee but not by much.

Real issue is they are serving it in US fountain drink cups (ie 32oz, 44oz, 48oz) rather than coffee sized cups (ie 8oz, 12oz, 16oz) and have caffeine concentration that aren't incidental (nutritional facts territory, ie from kola nut or tea leave food ingredients) but have crossed into where the FDA requires it be treated as a pharmaceutical product (like energy drinks) with supplement facts.

For coffee and other caffeinated beverages of similar concentration the largest serving container is always 16oz (large coffee cup, Rockstar, Monster, Bang) while the regular sized is 8oz (coffee cup, regular redbull) and medium is 12oz (standard coffee mug, large redbull). The FDA actually has guidelines on these serving sizes. Panera shouldn't have been serving this as a fountain beverage, no one else does for a reason and that reason being common sense in the protecting your business from liability.